Radiation detection devices that detect foreign substances, measure a component distribution, and measure weights, etc., in an in-line non-destructive inspection of a specimen that is conveyed by a belt conveyor or the like have been known. A radiation detection device includes a radiation detector having a scintillator layer and pixels, and detects radiation transmitted through a specimen and generates a radiation image.
This kind of radiation detection device is disclosed in Patent Literature 1. The radiation detection device described in Patent Literature 1 includes two radiation detectors with different pixel areas arranged side by side in a conveying direction of a belt conveyor. In this radiation detection device, large foreign substances are detected by the radiation detector with a larger pixel area, and small foreign substances are detected by the radiation detector with a smaller pixel area. By thus selecting a pixel size in advance according to a size of a foreign substance that a user desires to detect, foreign substance inspection accuracy can be improved.
As another method for improving the foreign substance inspection accuracy, a dual-energy radiation detection device has been known. A dual-energy radiation detection device includes two radiation detectors with different energy sensitivities, and detects radiation in a low-energy range (first energy range) and radiation in a high-energy range (second energy range) transmitted through a specimen. With this radiation detection device, a radiation image in a low-energy range and a radiation image in a high-energy range are simultaneously acquired, an image to which weighted subtraction and superimposition (for example, subtraction) is applied is created based on the radiation images, and according to a contrast difference in this image, a foreign substance is made to stand out, whereby realizing a foreign substance inspection with high accuracy.